Re: Oil viscosity recommendations?
Hi! I'm new to the forum, but v. much appreciate all the useful technical tips, etc. I especially appreciated the posts on noisy mid-'90s XJ distributors, which helped me decide to replace my '96 4.0 distributor last week right away after it started to squeal like a stuck pig at 92,00 miles. Too bad -- I've had many old engines that ran over 200,000 miles on the original distributor, with failure mode being too much play in the bushings and a bit shorter life on distributor caps, rotors, etc., not seized up bearings that cause internal engine damage when they fail!
I agree with the comment below about pre-HO 4.0 engines and their preference for heavier oils. I also have an '89 Comanche w/ 4.0 engine, which I have owned since it was new, and it has always seemed to do better on the heavier viscosity oils, at least in the 3 warmer seasons -- oil pressure runs higher at high temperature, and slight leak in rear main seal is minimized. After 16 yrs. and 212K of hard service with no engine work other than routine maintenance and an oxygen sensor and TPS 100K mi. back, I just passed strict Maryland emissions inspection with flying colors -- even better than 4 yrs. ago (mostly thanks to new factory catalytic converter, probably) -- order of magnitude better than State standards for '89 on all three criteria. I haven't done a compression test in a long time, but with those emission test results it must be o.k. -- so 15W-50 oil for 200,00 miles certainly hasn't hurt the older 4.0 engine...
On the '96 HO engine I have always followed the factory spec., which is 10W-30. I am v. curious to hear what others have to say about using heavier oils in that engine. Nearing 100K miles now, I would be tempted to convert to 15W-50, at least in warm season, as the engine develops some wear. What's even more interesting is that some newer engines (e.g, '05 Chrysler V6s) are now specifying 5W-20 oil, and dealer parts clerks are telling people that they will void their warranties if they use anything heavier than that. Very few aftermarket parts stores even sell 5W-20 oil... then I find out that when dealers' customers pay extra to have the service dept. change oil with "synthetic" they are getting Mobil 1 10W-30. What gives (other than what we already know, i.e., dealerships are often staffed by scam artists)?
xjnation said:
I never do any oil in any vehicle under 10-40, never have to me the 10-30 is a minium reccomondation. and most of what I use em in is highway vehices. It has just been my experience over the past 30 years of driving I get less engine wear and able to push the vehicles harder running heavier oil. shoot my 95 has over 220,000 miiles on it and still within 1% of original factory compression and the oil remains clean for about 2000 miles.
If I ran the reccomended 10-30 in our shelby glhs the oil pressure would never rise above 20 and knocks like a mofo. with 20-50 no knocking and 65 psi.
In the comanche 2.5 4 cyl I have little if any blowby into the air cleaner with 20-50 and about a quart a month with 10-30
anyone running an older pre HO xj will get much better results with a higher viscosity oil as requards to ail in the air filter. and will run smoother also. In my seat of the pants experience